Which dietary habits contribute to the development or prevention of rectal cancer?

Updated: Apr 06, 2021
  • Author: Burt Cagir, MD, FACS; Chief Editor: N Joseph Espat, MD, MS, FACS  more...
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Answer

A high-fat, low-fiber diet is implicated in the development of colorectal cancer. Specifically, people who ingest a diet high in saturated animal fats and highly saturated vegetable oils (eg, corn, safflower) have a higher incidence of colorectal cancer. The mechanism by which these substances are related to the development of colorectal cancer is unknown.

Saturated fats from dairy products do not have the same carcinogenic effect, nor do oils containing oleic acid (eg, olive, coconut, fish oils). Omega-3 monounsaturated fatty acids and omega-6 monounsaturated fatty acids also appear to be less carcinogenic than unsaturated or polyunsaturated fats. In fact, epidemiologic data suggest that high fish consumption may provide a protective effect against development of colorectal cancer. Long-term diets high in red meat or processed meats appear to increase the risk of distal colon and rectal cancers. [24, 25]

The ingestion of a high-fiber diet may be protective against colorectal cancer. Fiber causes the formation of a soft, bulky stool that dilutes carcinogens; it also decreases colonic transit time, allowing less time for harmful substances to contact the mucosa. The decreased incidence of colorectal cancer in Africans is attributed to their high-fiber, low–animal-fat diet. This favorable statistic is reversed when African people adopt a western diet. Findings of a meta-analysis of 22 studies with a total of 2,876,136 subjects suggest that dietary fiber intake could be a protective factor against rectal cancer with a clinically relevant reduction in rectal cancer risk. [24]

Increased dietary intake of calcium appears to have a protective effect on colorectal mucosa by binding with bile acids and fatty acids. The resulting calcium salts may have antiproliferative effects, decreasing crypt cell production in the mucosa. A double-blind placebo-controlled study showed a statistically significant reduction in the incidence of metachronous colorectal adenomas. [26] Other dietary components, such as selenium, carotenoids, and vitamins A, C, and E, may have protective effects by scavenging free-oxygen radicals in the colon.


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